Control valve for fluid operated engines for down well pumps



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CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25, l1955 11 Sheets-Sheety 3 LEGEND 55 POWER muxo 52 @E 54 EXHAUST bowN STROKE INVENToR. mum.) Roy H. De/r/ckson 5( X f K unlosnon *"1* BY, ENGINE Pls-rou uhuww QTTORNEYS Jan. 27, 1959 R. H. DEITRlcKsoN 2,870,749

CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25, 1955 11 Sheets-Sheet 4 SHIFTING ANNuLuS 55 LEGEND POWER FLum EXHAUQT 32 nwo ENmNE Y '29 PISTON H' I I I L INVENTOR.

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ArfoRNaY .2,870,749I CONTROL. VALVE FOR FLUID OPERATED ENGINES FOR DOWVNWELL PUMPS Original Filed Oct. 25, '1955 v R. vHDEITRICKsoN Jan. 27, 1959 ll 'Sheets-Sheet 5 PROOUCHON m W mm m y# md UJ TM .B Y

mi. F155 Jan. 27, 1959 R. H. pErRlKsoN CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL vPUMPS Original Filed Oct. 25, 1955 l1 Sheets-Sheet 6 l IN VEN TOR.

7/ O7/ f/M/ In.) X X 2 UP STRQKE To uNoERsmE oF ENG1-E Pls-rau HTTORNEYS Jan- 27, 1959 R. H. DEITRlcKsoN 2,870,749

CONTROL VALVE F OR FLUID OPERTED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25, 1955 11 Sheets-Sheet '7 EXHAUST FLLHD R0 H De/'fr/ckson l l y 5/ M mm. @Mw

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CONTROL VALVE:` FOR FLUID OFERATED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25, 1955 ll Sheets-Sheet 8 POWER FLL D EXHAUST CLUD x ITop nREVERSAL| x IN V EN TOR.

QTTURNE YS Jan. 27, 1959 R. H. DEITRlcKsoN 2,870,749

CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS v :Originavl Filed Oct. 25, 1955 l 11 Sheets-Sheet 9 LECQENQ Powe-R INVENToR. [j nog H. @ffmc/ 50 @du l @wS Jan. 27, 1959 R. H. plTRlcKsoN CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25, 1955 l1 Sheets-Sheet `1O u am 4 wl( X INVENTOR.

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CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS Original Filed Oct. 25. 1955 y 1l Sheets-Sheet 11 LEGEND POWER FLUID EXHAUST I n INVENTOR,

FLW? R05/ H. DE/r/cksan CONTROL VALVE FOR FLUID OPERATED ENGINES FOR DOWN WELL PUMPS Roy Deitrickson, Toledo, Ohio, assigner, by mesne assignments, to The National Supply Company, Pittsburgh, Pa., a corporation of Ohio Application April 18, 1957, Serial No. 653,622

23 Claims. (Cl. 121-150) This invention relates to an improvement in control valves for fluid operated engines employed in down well pumps.

This application is a continuation-in-part of my copending application Serial No. 542,582, led October 25, 1955, now abandoned.

The invention consists of a pressure actuated valve of the same general type as that shown in my United States Letters Patent No. 2,682,257, issued .lune 19, 1954 and, like the valve in that patent, a control valve embodying the invention takes advantage of changes in the pressure of the engine motivating fluid which occur near the top and bottom of the strokes of the engine piston to cause reversal of the direction of movement of the engine piston by shifting the control valve in response to such changes in pressure.

While the valve of my issued patent functions in general according to the preceding description and has the advantages and desirable operating features set forth therein, the control valve of the present invention has a further improvement relative to my patented valve which results from the elimination in the present invention of certain complex parts and subassemblies which are difcult to manufacture and assemble.

It is, therefore, the principal object of this invention to provide a control valve for a uid operated engine which is responsive to pressure variations caused by changes in the speed and position of the engine piston for throttling and reversing the uid connections to, and thus the movement of, the engine piston.

It is another object of this invention to provide a control valve for a fluid actuated engine of the type having a diiferential area between its upper and lower faces so that one face of the engine piston is exposed to high pressure Huid at all times and the other face of the piston is alternately exposed to high and low pressure uid for reversal of movement of the piston, the valve acting in response to changes in pressure occasioned by approach -of the piston to the limits of its stroke to alternately apply high and low pressure uid to this second face of the engine piston. l

It is yet another object of this invention to provide a control valve for a iluid actuated engine comprising a floating throttling valve responsive to changes in pressure of the fluid acting on one face of the engine piston during the movement of the engine piston between its extreme positions for maintaining a substantially uniform speed of movement of the engine piston even in the face -of changing load conditions.

Although the valve embodying the present invention will be described in the following specification in its Vapplication as a control valve for a fluid actuated downwell pump and is illustrated as constituting a separate unit attached to the upper-end of the engine cylinder of such a pump, neither its function nor its position is so limited. The valve must, of course, be in communication with a source of uid and with the enclosure to which the uid is to be directed in one valve position. In vthe embodiment of the invention disclosed for controlling av downwell pump, this enclosure is one end of the engine cylinder.

It is a broad object of the instant invention to provide an automatic alternate position valve, generally of the three-way type, to control the feeding of hydraulic lluid to one or more consumers wherein the valve position is automatically shifted in response to changing characteristics in theow to one consumer.

. As used in the following specification and in the claims, the term hydraulic force covers the summation of` hydraulic forces acting at any given time in any one direction. The hydraulic force can be created in either of two ways: first, by exposing equal areas to different and to oppositely acting pressures; secondly by exposing different areas to the same pressures. It should also -be noted that, as used in the following expression, the terms up and down,7 and other forms thereof such as upwardly, downwardly, upstroke and downstroke relate to the orientation of the embodiments described and are not limitations either upon the positions of otherembodiments of the invention or to be interpreted as limiting the invention to su'ch positions ,orl directions.

The foregoing brief description of the invention and some of its objects will be better understood by reference to the specication below and to the drawings, in which- Fig. l is a vertical sectional view of the upper end of a fluid engine for a downwell pump and particularly of one embodiment of pressure controlled valving mechanism embodying the invention; the parts being shown in the position occupied during an up stroke of the engine piston.

Fig. 2 is a vertical sectional view of the lower end of a fluid engine including the engine piston and its cylinder, the view being a continuation of Fig. 1 and depicting that portion of the engine next below the portion shown in Fig. l.

Fig. 3 is a view similar to Fig. 1 and including a portion of the structure shown at the top of Fig..2, but illustrating the moving parts in the position occupied during a down stroke of the engine piston.

Fig. 4 is a diagrammatic, vertical sectional View of that portion of the mechanism shown in Fig. 3 with the diameters of the various parts enlarged and their vertical dimensions diminished and illustrating the position of the parts during an up stroke of the engine piston.

Fig. 5 is a view similar to Fig. 4 but showing the parts of a control valve embodying the invention in the position occupied at about the time of atop reversal or change of direction of movement of the engine piston at the top of its stroke.

Fig. 6 is a view similar to Figs. 4 and 5 but illustratin the parts intheir position for a down stroke of the engine piston.

Fig. 7 is a view similar to Figs. 4, 5 and 6 but illustrating the parts of the control valve embodying the invention in the position occupied during a bottom reversal of the engine piston and also showing the engine piston at such position.

Figs. 8 and 9 are vertical sectional views similar in their relationship to the relationship of Figs. l and 2 and particularly illustrating a modified form of control valve embodying the invention, the parts being shown inthe positions just after a bottom reversal of the engine piston and before the start of an up stroke thereof. Y

Fig. l0 is a view similar to Fig. 4 but of the embodiment of the invention illustrated in Figs. 8 and 9, showing an up stroke.

Fig. ll is a view similar to Fig. 5 but of the embodiment of the invention illustrated in Figs. 8 and 9 at the time of-a top reversal.

Fig. 12 is a view similar to Fig. 6, but, again, ofih -3 second embodiment of the invention, i. e., that structure illustrated in Figs. 8 and 9 during a down stroke.

Fig. 13 is a View similar to Fig. 7 but illustrating the structure shown in Figs. 8 and 9.at bottom reversal.

p Fig. 14 is a View similar torvFig. -4 but illustrating a modification of the structure embodying the invention.

'ENGINE CONSTRUCTION A control valve embodyingthe invention is intended to be Vemployed witha fluid actuated engine for a downwell pump of the general type vthat is at or near the bottom of a well casing fragmentarily indicated in Fig. 1 by the reference numeral20. The casing Ztl-is shown in Fig. 1 Aonly butit is to be understood throughout the description of the figures that the entire pump mechanism 'including lits own yengine casing 21 is located within the continuous 'well 'casing or tubing 2i). vIn illustrating the engine of thegdow'nwellpump `it will be assumed that ythe pump itself is of the type well known in the art which discharges its production huid, i. e., `the crude oil drawn from the formation, into the annular space generally indicated yat 22 in Fig. 1 exteriorly of the engine cas-ing 21 and interiorly of the well casing or tubing 20. The

annular space 22 extends from the exterior of the Vpump `at the -bottom of the casing to the surface and the production fluid as well as discharged engine actuating fluid is carried to the surface in the annular space 22, sometimes called the production annulus.

AA downwell pump of this general type has an engine casing 21 inside of which there is located a valve jacket 23, the upper end 'of which is closed by an upper cross head block generally indicated at 24, the cross head yblock 24 being threaded into the upper ends of both the engine casing 21 -and the valve jacket 23 at the places indicated by the reference characters 25 and 26, respectively in Fig. 1. The valve jacket 23 has an outer diameter less than vthe inner diameter of the engine casing 21 which leaves a power fluid annulus 27 extending the length of the exterior of the valve jacket 23 and the length of the exterior of an engine cylinder 28 (Fig. 2)

of the Asaine diameter as the valve jacket 23 but extending downwardly below the valve jacket 23 and forming a cylinder for an engine piston generally indicated at 29 in Fig. 2.

The engine Apiston 29 is connected by a piston rod 30 (Fig. -2) to a pump piston, not shown in the drawings, but connected to the engine piston 29 and operating in the manner similar to the engine and pump pistons shown in my Patent No. 2,682,257. It will be observed in Fig. v2 that'because of the presence of the connecting rod 30 which vextends downwardly out through the bottom of the engine cylinder (see Fig. 7) the sum of the areas on'the upper surface 31 of a cylindrical tenon 32 on the top of the piston 29 and an annular shoulder 33 Von the piston 29 is greater than the sum of the areas on db'wn strokes -of the pump piston connected thereto by the -rod' 30.

In ann engine of this type it is necessary, therefore, `only to valve the engine cylinder 28 above the piston '29'to both high and vlow pressure lines leaving the engine cylinder 28 below the lpiston 29 permanently connected to the :high vpressure actuating huid.

High pressure actuating fluid is led downwardly from the surface to an engine of the type being discussed "through a'string of high pressure macaroni connected to ahigh pressure 4vsocket 37 (Fig. l) at 'the top of the upper cross head block 24. The vfso'cket 37 connects @through -a Aplurality of vpassageways 38 with the'fpower annulus 27 to lead power uid down the exterior of the valve' jacket '23 to the bottom Vof the 'engine 'cylinder 28 (Fig. 7) and through a plurality of radial passageways 39 into the engine cylinder 28 beneath the engine piston 29. Power fluid may also be admitted into the interior of the valve jacket 23 through .a `plurality of radial ports 40 (Fig. 1) which register with radial ports 41 in a tubular valve liner 42, depending upon .the position of a spool valve Agenerally indicated at 43.

The lower end of the Valve jacket 23 isvthreaded onto the exterior of a socketed plug 44 (Fig. 2) which also delineates the upp'errend of the engine cylinder 28 and is eounterbored forming an upper dashpot 45 which receives the Vtenon'32 on the upper end .of the engine piston 29 when the engine piston 29 reaches the top of its stroke (Fig. 5).

The upper cross head block 24 also connects the production annulus l22-through acenter bore'46 and a plurality of radialpassageways 47 to-an upper valve cham ber V48 interiorly of the Valve jacket 23 and above the valve-liner 42.

VALVE CONSTRUCTION The valve liner 42 is 'positionedy in Vthe valve jacket 23 at its upper end by a retaining ring 49 set 4upon `a suitable groove in the interior-of the valve `jacket 23 and axially abuts the 'upper end cfa valve restrictor sleeve 50Y1(Fig. l) which rests on lthe upper surface of the plug'44 defining -a lower valve chamber 51. The valve restrictor sleeve 50 Ahas a vertically extending annular land 52 which cooperatesl with a bulbous spool vvalve head 54 integral'lymounted 'onthe lower'end' of-a spool valve body 55. The spool valve body S5 is axially boredtol form a continuous verticali-passageway 56 opening into the upper valve pocket S1-at its flowerend andintersected by two spaced sets :of `radialvpor-ts S7Land'158.

*Thefupperfend of :the 'spoolvalve-body 155 extends into a `guidey 'cylinder- 59, having a-` relatively snugsliding -it therein,-lthe twowforming 4a vvalvestem pocket 6G. The guideY59-1is 'thrust Iupwardly by a coil retaining#spring 61 against the sphericallower endi 62=of t'he'upper cross head block 24. The fre'edorn io'f movement provided by the retaining Springftll thrusting thefcylinder259 Magainst the-spherical end 162rpermits some 4lateral-play inthe vertical :movement *of :the vspool 'valve body` 55. =lfl the `cylinder f59 were :formed .integrally vwithf lthe A'lower end of the upper cross headfblo'ck, -for example, since -theupper end of the :spool valvebodyfSS slides lintoand out y'of the cylinder V59, .all A'ofi-these cooperating parts would have-,to be machined fand :assembled with great accuracy. Since the upper cross 'head block l24 .i s Athreaded -into thefupper-endof the v'alve --jacket 23 itiwould 'be almost-impossible to maintaina .socket in the -lower end of the-cross-h`ead block 2li-close enough fto perfect con- -c/entri'city 'withithe valve- 'liner-"42 tovpermit this faction. `r11: should be observed'in 1lFig. -1 y'that -the Vertical distance Ybet-Weenthe'vupper edge of ani-'annular groove 53 that is intersected by the radial ports 58 andthe lower edge of asimilar annular groove l64 vintersected by the ports 57 is -less- 'than 'the Vertical -dis'tance between the upper edge of an annular groove h5 in "the valveliner42 that is intersected-by the passageways j141 andV a shoulder on the upper end ofthe 'valveliner '42. Thus konly 'one ofthe setsof ports 57 and SScan be placed in registry with*thehigh'pressure ports lillortlie upper valve chamber 48, respectively, at a time.

The maximum diameter 'of the bulbous spool head 54 :is slightly less than lthe minimum diameter of the land `52 in the valve restrictor sleeve Si). The bulbous spool head 54 tapersfin both directions away lfrom this surface of maximum diameter.

The construction just described provides a variable 're- `striction i(between thefhead 54 -and land'SQ.) to the flov/ of "fluid to ftheupper 4end 'of'the engine cylinder' Sand the "pressure` Vldropthrough fthe restriction provides lthe second hydraulic `force for holding the valve body 55 in this first, lower position. Although the restriction in this embodiment of the invention is variable, in order to provide for automatic balancing of fluid flow and pressure as will be described below, variability is not necessary. The restriction may be of fixed size andneed only be of such size that fluid ow at a rate above a-predetermined rate causes a sufficient pressure drop across the restriction so that the second hydraulic force overcomes the rst biasing force and holds the valve in its rst position. Similarly, the particular location of the restriction is not critical. It need only be in the uid ow path and effect some portion of the shiftable valve body 55 either directly, as where the valve body 55 itselfconstitutes part of the structure forming the restriction, or indirectly.

In the embodiment illustrated in Figs. l-7, the annular space between the periphery of the head 54 and the land 52 constitutes the restriction. The pressure drop around the head 54 creates the secondhydraulicl force for holding the Valve body 55 in position (see Fig. 6). If the further improvement of variability is not desired, the restriction can be formed by drilling a passage 53h (Fig. 14) of suitable size axially through the head 54h (in place of the angular openings shown as leading from the central passageway 56 in Figs. l-7) to the lower valve chamber 51h. In this variation, a head 54h is cylindrical and has sliding contact with a cylindrical land 52b on the inner wall of the sleeve 5017.

VALVE OPERATION Up stroke Referring now to Figs. l, 2 and 4 which illustrates y the position of the valve embodying the invention and the engine piston 29 during an up stroke of the engine piston 29, the operation of the control valve embodying the invention will be described. p In Figs. 1 and 4 the spool valve SS is shown in its nearly uppermost position in which the radial ports 58 are completely open to the upper valve pocket 48 and thus the vertical passageway 56 through the spool Valve 55, the lower valve pocket 51 and the engine cylinder above the engine piston 29 are in communication with the low pressure exhaust and production fluid annulus 22. Since the space in the engine cylinder 28 beneath the piston 29 is continuously in communication through the power annulus 27 with the power fluid line from the surface, high pressure power fluid is fed into the engine cylinder 28 beneath the piston 29. Even'though the bottom area of the piston 29 is less than its top area (summation above) the considerable difference in the pressures of the power fluid and the production uid drives the piston 29 upwardly. The low pressure fluid above the piston 29 escapes through the path described as the piston 29 moves upwardly.

It will be observed more clearly in Fig. 4 that even though the lower valve pocket 51 and the space in the engine cylinder 28 above the piston 29 are in communication with the exhaust annulus 22, an annular shoulder 67 formed by a reduction in the diameter of the spool valve body 55 is exposed to high pressure fluid in the radial ports 4l and 40 in the valve liner 42 and valve jacket 23. The high' pressure fluid acting on the shoulder 67 creates a rst hydraulic force biasing .the valve body 5S downwardly.- Its action, therefore, tends to thrust the valve body 55 down out of the position illustrated in Fig. 4 and there is no other high pressure area on the spool Valve 43 or its bulbous spool head 54 during the up stroke of the engine piston. The first downward biasv amm 6 cient to hold the spool valve body in its upper position as shown in Figs. 1 and 4.

Power fluid continues to flow down the power uid annulus 27 and exhaust fluid continues to be forced out of the engine cylinder V28 through the passageway 56, radial ports 58 and upper valve pocket 48 to the exhaust annular. passageway 22. As long as asubstantial flow continues through the annular restriction around the head l 54 the'second holding hydraulic force holds the body 55 in position against the-first biasing hydraulic force.

Top reversal As the piston 29 approaches the upper limit of its stroke (Fig. 5) the upper tenon 32 enters the dashpot 45 which greatly restricts the escape passage through the dashpot 45 for the remaining quantity of uid in the engine cylinder 28 above the engine piston 29. The reduction of llow of exhaust fluid out of the lower valve pocket 51 through the restriction past the spool valve head 54, reduces the hydraulic force resulting from the pressure drop around the head S4, so that the biasing force created by the high pressure fluid acting on the shifting annulus 67, thrusts the spool valve body 55 downwardly. At the same time the pressure ofthe iluid in thelower valve pocket 51 is raised to an intermediate value and, almost immediately after the spool body 55 starts downwardly and closes the radial ports`58, the lower radial ports 57 are opened to the high pressure ports 41 from the power fluid annulus 27 and high pressure oil enters the interior passageway 56 of the spool valve 43 and the lower valve chamber 51 above the bulbous head 54. High pressure iluid completely lills the lower valve chamber 51, the passageway 56 and the upper valve stem pocket 60 and the only portion of the spool valve body 55 which is not exposed to high pressure uid, is a second upper annular shoulder 68 which is stillexposed in the upper valve chamber 48 to the lower pressure of the production and exhaust fluid permanently in that chamber. The sum of the forces acting on the spool valve body 54 is thus balanced out except for the difference between the low pressure acting on the annular shoulder 68 and high pressure fluid acting on a similar annular area on the undersurface of the bulbous spool valve head 54. This net resolution results in a yslightly upward hydraulic force acting upon the spool valve body 55 to bias it upwardly. This force isovercome by a second holding force resulting from the flow of iluid which now ows downwardly through the restriction formed by the head 54 and the restrictor land 52 (see Fig. 6) and creates the second hydraulic holding force.

i Down stroke With the spool valve 43 having been shifted to its lower position as illustrated in Figs.l 6 and 3, the ow of fluid downwardly through the restriction around its bulbous head 54 counteracts the biasing force caused by the pressure differential on the annulus 68 and tending to move the spool valve body 55 upwardly. The holding force created by the restriction overcomes the biasing force and valve body 55 remains down in its lower position during the down stroke of the engine piston 29 as long as more than a predetermined flow of liquid to the engine cylinder 28 continues. Power fluid from the power fluid annulus 27 flows inwardly'through the ports 40, 41 and through the ports 57 into the center passageway 56 in the valve body 55, through the restriction around its bulbous head 54, through the lower valve chamber 51 and into the upper end of the engine cylinder 28 above the engine piston 29. This lforces the engine piston 29 downwardly even though the space in the engine cylinder28 beneath the piston 29 is also exposed to high pressure operating fluid because of the differential area between the upper and lower faces of the piston 29. As the piston 29 moves downwardly, high pressure fluid beneath the piston 29 Vis discharged radially outwardly through the passageways9, Fig. 7 (not shown in Figs. 3 and 6) and upwardly through the4 power fluid annulus 2 7, being displaced from beneath the engine piston 29 to above the engine piston 29. During each down stroke of the engine piston Z9 a volume of power iluid equal to the volume of the piston rod in the engine cylinder 28 beneath the piston 29 must be added from the power fluid source to effectuate the down stroke. The remainder of the volume in the engine cylinder 28 above the piston 29 is supplied by power fluid displaced from beneath the engine piston 29.

Except for its movement reecting gassing conditions and/orrother fluctuations in load or pressure, the spool valve body 5S is held in its lower position shown in Figs. 3 andv 6 by the second hydraulic force created by the restriction `and until :the engine piston 29 approaches the lowermost end of its travel and the tenon enters a lower dashpot 69 (Fig. 7) yat the bottom of the engine cylinder 28.

Bottom reversal jAs is shown in Fig. 7, when the tenon 35 enters the dashpot 69 the only escape passage for the uid beneath the engine piston -29 is the small annular space between the tenon 35 and the inner wall of the dashpot 69. Limiting the escape of this uid acts to slow down the movement of the engine piston 29 downwardly and to increase the pressure in the engine cylinder 28 above the piston' 29. Slowing down the downward movement of the engine piston 29 also reduces the ow of iluid downwardly through the restriction around the spool valve head 54 and the second hydraulic holding force created by the pressure drop through the restriction and acting to hold the spool valve body 55 down, no longer exists. It should be noted, at this point, that other means for reducing the flow of iluid through the restriction could also be ern-` ployed. As a variation, for example, a member carried by the engine piston 29 might act to reduce the ow of fluid as by gradually closing the power fluid ports 4l) or 41. High pressure now acts over the entire undersurface of the head 54 and since lower exhaust pressure is present on the annulus 68, the sum of the biasing hydraulic forces on the spool valve body 55 is upward in direction and the spool valve body.55 is moved upwardly. As the valve body 55 moves upwardly to the position illustrated in Fig. 7, the ports 58 pass lthe upper shoulder 66 of the valve liner 42. The internal passageway 56 of the spool valve body 55 and thus the lower valve chamber 51 and the space in the engine cylinder 28 above the piston 29 are vented to the upper valve chamber 48 so that the pressure above. the engine piston 29 drops immediately to an intermediate pressure as shown in Fig. 7 and then, as the valve body 55 continues to move upwardly to its up stroke position, the pressure in the system above the engine piston 29 falls tothe exhaust pressure and the valve reaches the position illustrated in Fig. 1 to commence an up stroke of the engine piston 29.

Gassing conditions `When, as frequently occurs, there is gas present in the formation, the single action pump driven by the engine controlled by the valve of the invention draws gas into the pump cylinder beneath the pump piston on 'an up stroke. .On the next down stroke of the pump piston under such conditions the gas is merely compressed and does not exert suicient lift against the travelling valve 7 embodying the invention when gas is present beneath the i pump piston and the engine piston tends to speed up because of the mentioned load on the pump piston, the

rate of How of fluid aroundthe spool valve head 54h1- creases because Vof the reduced pressule beneath the head 54. Whenever the rate of flow of fluid around the head 54 increases and also because of the reduced pressure beneath the head 54, the pressure drop across `the annular orice between the head 54 and the land 52 also increases and this increase in pressure differential moves the valve head 54 and the spool valve 43 downwardly.

VWhen the valve ,43 moves downwardly it throttles the high pressure ports 40-41 which reduces the rate of ow of the power uid from the power lluid annulus 27 into the interior passageway 56. Reduction of flow of the high pressure uid into the interior of the valve body 55 compensatingly reduces the quantity of the fluid iiowing around the bulbous head 54 and the input owl of high pressure power iiuid to the upper end of the engine cylinder 28 and slowing the downward movement of the engine piston l2.9.

Sand in pump It 4frequently happens that ne sand from the formation enters the pump. Any such sand which enters the pump cylinder tends to work into the close space between the pump piston and the inner wall of the pump cylinder and its presence, of course, makes the pump piston stick or bind. When this occurs in a pump having a tixed length of stroke through which the pump piston must travel before its control valve can be actuated (for example, garbutt rod controls) the pump piston is stopped by the binding before it has traveled far enough to actuate the valve, which locks up the pump and causes serious damage.

In a pump controlled vby a control valve embodying the invention no damage occurs to the pump mechanism or to the engine mechanism when sand enters the pump. For example, if sand enters the pump during an up stroke (Fig. 4) the presence of the sand retards the movement of the pump piston. This stops the` movement of the engine piston 29 and decreases the rate of ow of exhaust fluid around the bulbous head 54. This drop in rate of ilow reduces the pressure drop around the bulbous head 54 so that the high pressure Huid present on the shifting annulus or lannular shoulder 67 comes into play and thrusts the spool valve 43 downwardly, reversing the movement of the engine piston by admitting high pressure fluid into the system` as in Fig. 6 t0 produce a down stroke carrying the pump piston away from the sand.

Similarly, if sand enters the pump cylinder during a down stroke (Fig. 6) the movement of the piston downwardly stops. This increases the pressure above the engine piston 29 and thus in the systeml controlled by the spool valve 43 and equalizes the pressure on both sides of the bulbous head 54 so that extremely high pressure is acting on the underside of the bulbous head 54 over the annular area corresponding to the annular shoulder 68 which remains exposed only to the low exhaust pressure. The net balance of forces present on the spool valve body 55 is thus in an upward direction and the spool valve 43 is moved upwardly, as at a bottom reversal, to the up stroke position of Fig. 4.

SUMMARY OF VALVE OPERATION From the preceding description of the operation of the valve particularly under the headings Top Reversal, Bottom Reversal, Gassing and Sand, its operation will be seen to be -controlled by the balancing and unbalancing of the biasing hydraulic force which results from exposure of equal valve body areas to different pressures or dilerent valve body areas to the same pressures, against a holding hydraulic created at the ow restriction. Decreases in the ilow of fluid through the restriction below a certain level reduce the second holding force to a point such that -the biasing force causes the valve body to shift. In addition, because the restriction 'engine cylinder 21a and valve jacket 23a.

in the illustrated embodiment of the invention is variable, minor increases or decreases in the rate of ow produce corresponding liuctuations of the position of the valve body 55 which throttle or open the flow of uid through the passageways 57 and 58. It therefore follows that any change in the rate of ow through the restriction and compensating change in the second holding hydraulic force, whether brought about by actual changes in the load on the pump piston or artificial changes in the load resulting from approach to the ends of strokes, results in an 'automatic shift of the control valve to produce a correct change of movement of the engine piston 29.

Modification two The modification of the invention illustrated in Figs. 8-13 primarily consists of changes in the valve restrictor sleeve and in the provision of fluid metering means at the upper end of the valve spool body. In describing the embodiment of the invention in these figures, therefore, like numerals having the sutiix a will be given to parts in Figs. 8-13 which 'are identical to parts in Figs. 1-7 and new reference numerals to those parts which are different in structure or function.

In common with the modification of the invention illustrated in Figs. 1 7, the embodiment of the invention illustrated in Figs. 8 and 9 has an upper cross head block 24a which is threaded into the upper end of a valve jacket 23a and into the upper end of a larger engine casing 21a. The cross head block 24a has a high pressure socket 37a at its upper end which communicates through a passageway 38a with a high pressure annulus 27a between the The upper cross head block 24a also has a center bore 46a cornmunicating through radial passageways 47a with a production tluid annulus 22a between the exterior of thel engine `casing 21a and the well casing 20a only fragmentarily shown in Fig. 8.

At its lower end the center bore 46a communicates with an upper valve chamber 48a. In this embodiment of the invention the upper valve chamber 48a is formed between the interior of the valve jacket 23a andthe exterior of a tubular valve stern cylinder 70 (Figi. 9) at the lower ends of which a plurality of radial ports 71 are located. The radial ports 71 are positioned relative to a spool Valve 43a and two upper spool valve ports 58a and their connecting annular groove 63a, in the same manner as the upper shoulder 66 of the embodiment of the invention illustrated in Figs. 1-7. In Fig. 9 the lower edge of the port 71 is designated by the reference number 66a to indicate this similarity.

The spool valve 43a has a generally tubular body 55a through which extends a center vertical passagewayl 56a into which the ports 58a lead, as well as similar ports 57a. -The diameter of the spool valve body 55a is stepped down forming a high pressure annular shoulder 67a just below ports 41a in a tubular valve liner 42a, the ports 41a being aligned with ports 40a in the valve jacket 23a and thus in constant communication with the high pressure annulus 27a. A similar step down i'n diameter forms an upper annular shoulder 68a so located as to be constantly subjected to exhaust fluid pressure in the ports 7ll.

At its lower end the valve spool 43a has a bulbous head 54a which is located in a lower valve chamber 51a and which cooperates with an annular land 52a on a vertically movable restrictor sleeve 72. The restrictor sleeve 72 Iof the instant embodiment is functionally identical with the restrictor sleeve 50 of the embodiment of the invention illustrated in Figs. l-7 but is verticallymovable for a purpose to be described below by a friction ring 74 set into the spool valve body 55a and bearing upon the inner surface of the restrictor sleeve 72. The restrictor sleeve 72 is shorter than the distance between the lower end of the valve liner 42a and the upper end of a plug 44a which defines the bottom of the lower spool valve `chamber 51a and the top of an engine cylinl() der 28a so that the restrictor sleeve 72 moves between an upper position in contact with the lower endv lof the l valve liner 42a (Figs. 9, l0 and 13) and a lower position in contact with the upper end of the plug 44a (Figs. 1l and l2). Like the plug 44 (Fig. 2) the. plug 44a also denes an upper dashpot 45a for the reception of an upper tenon 32a (Fig. l0) on the top of an engine piston 29a.

The upper end of the valve body 55a above the annular shoulder 68a slidingly tits into Ythe cylinder 70 at the lower portion thereof and the bore of the cylinder 70 is enlarged at its top forming a valve stem pocket 74 in which the upper end of the valve body 55a loosely fits. The upperpend of the valve body 55a, i. e., that portion above the shoulder 68, is generally referred to as a valve stern 75.

The valve stem 75 has a plurality of passageways connecting the passageway 56a with the upper valve stem pocket 74. These passageways include an axial vertical passage 76 leading upwardly through the center of a valve stem plug generally indicated at 77. Thev passage 76 leads to a pocket 78 in which is located a spring biased plunger 79 that bears upon a ball 80 normally seated at the bottom end of a `continuing axial passageway 81 in the plug 77. The plunger 79 is movable in the pocket 78 but -does not interfere with the `flow yof liquid therethrough. Radial ports 82 connect the passage 76 with an anular` space 83 Vsurrounding the lower end of the valve stem plug 77. The space 83 communicates through radial ports 84 with the pocket 74. The passage 76 is also connected through the pocket 78 by radial ports 8S with the radial ports 84 and the pocket 74. Continuing up the valve stem plug 77, the passage 81 is connected by radial ports 86 and 87 to the pocket 74 and a second ball 88 normally is positioned to close the upper end of the passage 81. A stop block 89 in the uppermost end of the valve stem plug 77 limits the upward travel of the ball 88 and the passage 81 continues beyond the ball 88 around the block 89 to the upper end-of the pocket 74.

It'is thus possible for lluid to move between the passageway 56a and the pocket 74 through several alternative and/or simultaneous paths,viz.: (a) ports S2, space 83, port 84 and, simultaneously, passageway 76, socket 78, port 85 and port 84. is `down from the position shown in Fig, 9, passage 81 and ports 86 and 87. (c) In'addition, when the ball 88 is raised from the position shown in Fig. 9, continuation of passage 81 past stop block 8,9.

In Fig. 9 the spool valve 43a, valve body .55a and restrictor sleeve 72 are shown in the position which those parts assume just after a bottom reversal has caused the valve 43a to move upwardly a distance sufficient to move the restrictor sleeve 72 up against lthe bottom end of the valve liner 42a, but before the valve 43a has moved up enough to align the ports 58a with the ports 71 to produce an up stroke.

Up stroke Fig. l0 illustrates the valve 43a and restrictor sleeve 72 in the up stroke position to which they move after the position shown in Fig. 9. When the valve 43a is in this uppermost position, the ports 58a are aligned with the ports 71 at the bottom of the 'upper valve stem chamber 48a to permit the escape of exhaust engine uid yfrom the space in the engine cylinder 28a above the piston 29a through the central passageway 56a of the 4spool valve 43a. As in the earlier .described `embodiment of -the invention, power tluid moving down the power luid annulus 27a to the underside of the engine piston 29a moves the piston 29a upwardly until its upper tenon 32a enters the upper dashpot 45a. During this movement, the cene tral passageway 56av and all of the passageways and ports in the valve stem 7S and valve stern plug 77 are tilled with exhaust engine uid.

(b) In addition, when the ballv zfsvzoyme Vl i Top reversal lWhen'the up'per tenon 32a enters the upp'er dashpot 45u the insertionfof the tenon 32a into 'the dashpot 45a reduces the flow of escaping fluid from above the engine piston 29a which reduces the velocity of the fluid around the spool head'Sla and the pressure differential acting to hold'the spool valve 43a up. When this occurs the high pressure force acting upon the annular shoulder 67a moves the valve 43a' downwardly. Because of the. drag of the friction ring 73 the valve body 55a carries the restrictor sleeve 7'2 downwardly to its lowermost position indicated in Fig. 1l. This movement of the restrictor sleeve downwardly accomplishes two purposes, first it moves the land 52a downwardly to cooperate with the bulbous head '5'4a when the valve 43a is in its lower position. fluid in'the lower valve chamber V51a occasioned by movement of fthe valve `bo'clyVSSa downwardly thereinto'.

Because of the influx of high pressure fluid when the ports 51a are first opened to the high pressure ports 10a-41a and lhigh pressure fluid is admitted into the central passageway 56a, the pressure rises rapidly in the passageways in the valve stem 75 and the valve stem plug'77. This lifts the upper ball 88 from its seat and opens a pathway for the high pressure fluid through the ports 82, 85 and 84 to the valve stem pocket 74 and back throughfthe ports 87 and 86 and through the passage 81 past the ball -88 into the upper portion of the pocket 74 above the valve stem 75. At this point the parts are in the position shown in Fig. l1.

l From the position shown in Fig. l1 to fully open position the travel of the spool valve 43a downwardly is'relatively slow and it only graduallyopens communication between the high pressure -ports '40u-41a and the ports 51a leading to the interior passage 56a of the spool valve body 55a. This reduction in speed of downward travel is under the control of a land 90 formed on the valve stem 75 which begins to close an annular space surrounding the land l90 and between it and a shoulder 91 on the walls of the valve sterncylinder 70 at the bottom of the pocket 74. Closing this pathway around the land 90 reduces the flow of fluid into the pocket 74 in the interior of the cylinder 70. Simultaneously and as the high pressure ports 51a and 10a-41a are opened the bulbous head 54a enters the narrowest restricting portion of the lrestrictor sleeve 52a. Further downward movement of the valve 43a finally fully inserts the land 90 into the smaller diameter portion of the cylinder 7u at the shoulder '91 restricting the flow of fluid through the port 84 to cut down the rate of flow into the pocket 74 so that the movement ofthe spool valve 43a downwardly continues at a slow r'ate of speed until it reaches its bottom-mostposition which it occupies during a down stroke.

Down stroke Gssing n down stroke ln the case of a gas condition as described earlier, the reduction of pressure in the engine cylinder 28a above the engine piston 29a reduces the pressure differential around the head 54a and lowers the spool valve 43a to throttle the high pressure ports 40u-41a and 51a.

Secondly, it compensates for the displacement of Anytendency ofthe spool valve 43a to Vhunt as a result 'of changes in pressure accordingly due to gassing conditions or to other variables, is throttled and virtually eliminatedr by the damping effect of the restricted space between theftanu arid the fshbtder 91 since "the `4spool valve `?43a"cannot fr'eely rnoveiup and fdown unless fluid can freely 'flow `into-and fout of th'e pocke't 74. With the lower balll'tlt in its nomal'positionas illustrated in Fig. l2, the only D'pathway 'ffor fluid -IAinto the pocket 74 is around rtheiland l90.

"lhus underlnorm'al'or other conditions the ypiston y29a continues -to move downwardly until, as in the case of the embodirnentlof iFigs. 'l-7, it reaches the bottom of th'e engine cylinder and bottom reversal occurs.

Bottom reversal When the lower tenon-Sa (Fig. l13) enters the lower dashpot 69a reduction in flow of fluid from beneath the engine piston 29aibuilds-'up the ffluid pressre-abovethe engine piston 29a `and,as 'in the case ofthe ifi'rsbembodiment ofthe invention, the greater "pressure V#beneath the spool Ivalve 43aovercome's the lesser pressure actingon the .upper shoulderf'68a tor-move the spoolvlve-43a upwardly. As 'the spool valve body 55a moves upwardly the friction ring -73"dra'gs the restrictor sleeve 72 lto its upper :position (Fig. '13). This fportion ofthe upward travel of the spool `valv'e"'43 lis relatively fast because of the high pressure lluidft'r'app'e'd vin the lpocket 74 which rushes 'through 'the ports l87, 86 and passage 8l to Ashift the flower ball Stb-downwardly opening vall'of the passages through the valvestem plug 77 to allowthis fluid to escape.

Fromthis pointlon the travel of the spool valve 43a tolits fully -openfupper position will be slow. Since -the restrictor :sleeve 72 lhas been moved upwardly, as the head 54a moves upwardly 4it'enters the narrowest portion ofthe sleeve 72vat 'the land 52a and alsdan-'enlarged head 92 on the uppermost end of the valve stem 75-en ters a restricted portionf93-at the top ofthe cylinder'7tl. The pressure :beneath the spool valve 43a lpushes the valve upwardly and the restriction around the enlargef menti92prevents the rapidescape of theiflu'id from above the valvefstem'75. When'the valve- 43a hasmovedupwardly a sufficient distanceto open the escape ports '5&1 to the eXhaust port 71 the pressure in the 'fluid above the engine piston 29a drops and thevhigh pressure fluid-beneath the engine piston Z'Qajthough acting rupon its smaller bottom area, moves theengine piston 29a linto'anup stroke.

Sanding conditions lncommon with the 4modification ofthe invention described above with reference to Figs. 1 7, inclusive, entry of sand into the pump cylinder effects the appropriate reversal by a pressure'action ri-dentical to that occurring at the limits of theup .and down strokes.

'In certain of the followingy claims the word consumer is employedto'denominate the means utilizing-.or consuming thetpower fluid being -controlled by a'lvalvek ern- -bodying ythe invention. Thefconsumer in the specific modifications of the invention illustrated in the drawings is, of course,'the engine itself, ire., the power fluidis consumed'by the engine in order'to'move itspiston tol accomplish the ywork done by the pump.

What I claim is:

l. In a fluid operated downwell pump comprising a pump cylinder, an engine'cylinder longitudinally displaced from said pump cylinder, connected-pistonsoperating in the `respective pump and engine cylinders, saidengine piston having a greater-effective areaxon'one side Vthan on the other whereby equal operating. pressures on its two faces causemovement thereof in one'directioman exhaust passage, and a source of operating fluid under pressure, the improvement comprising Valve mechanism including a housing having allow chamber locatedabove and in constant communication with the end of lsaid engine cylinder above said engine -piston,-.a constantly a port in said housing to saidexhaust passage, a port in said housing to said source of operating fluid, a valve in said housing for alternately connecting said ports to the upper 'side of said flow chamber, an roperatively integral head on said valve extending l'down into said llow chamber, and'means insaid flwchamber cooperating with said head for forming a variable'llow passage through said chamber'forestablishing a pressure differential on opposite sides of said head.

2. Mechanism according `to, claim vl in which said means in said flow chamber vcooperating with said head is a land on the wall of said flow chamber so located as to form with said head an annular opening Variable in cross section as said valve and saidy head move vertically.

3. Mechanism according to claim l and a shoulder on said valve that is constantly under operating fluid pressure for biasing said valve toward position for'connecting said source of operatingiluid to saidv flow chamber.

4. Mechanism according to kclaim .3 and a second shoulder `on said valveI that is 'constantly under exhaust lluid pressure acting in the same direction as the first said shoulder. v r

i 5. Mechanism according to claim l in which said valve is a spool valve and there is a dashpot at the upper end of said valve, and said valve has a vertical passageway therethrough placing said llow chamber in communication with said dashpot. Y

6. In a lluidv operated downwellr pump comprising a pump cylinder, an engine cylinder longitudinally displaced from said pump cylinder, connected pistons operating in the respective pump and engine cylinders, said engine piston having a greater effective area on one side than o n the other whereby equal operating pressures on its two faces cause movement thereof in one direction, an exhaust passage, and a source of operating fluid under pressure, the improvement comprising a constantly open passageway between the side of said engine cylinder beneath said engine piston and said source of operating uid, a valve housing, ports in said housing leading to said source of operating lluid and to said exhaust passage, a llow chamber at the lower end of said valve housing and opening to said engine cylinder above said engine piston, a tubular valve in said housing slidable vertically between a position placing said 'source of operating fluid in communication with said ilow chamber and a position placing said ilow chamber 'in communication with said exhaust passage, a head on said valve extending into saidy flow chamber, and at leastone land on the 'wall of said flow chamber and cooperating withsaid head to form an annular passage vof variable cross section, the vertical position of saidhead and said valvebeing responsive to variations in the pressure differential in the fluid on the upper and lower faces of said head caused by low of lluid into and out of the upper end of said engine cylinder and through said lloW chamber.

7. Mechanism according to claim 6 in which said valve has an annular shoulder constantly subjected to operating fluid under pressure for biasing said valve and said head toward the lower position thereof in which said source of operating lluid is in communication with the upper end of said engine Acylinder through said flow chamber.

8. Mechanism according to Vclaim 6 in which the land on the wall of said flow chamber is formed on the inner wall of a vertically shiftable sleeve surrounding said valve and there are drag means located between said valve and said sleeve-for shifting saidl sleeve and said land slightly in the direction of movement of said valve at the beginning of such movement.

9. Mechanism according to claim 6 in which said housing has a dashpot at the upper end of said valve and said dashpot communicates through the inner passage of said tubular valve with said flow chamber.

l0. Mechanism according to claim 9 in which there are variable restrictions at the top of the center passage of said tubular valve for controlling the rate of ilow of iluid between the dashpot and the inner passage of said tubular valve upon vertical movement of -saidpvalve and the upper end thereof into and out Iof said dashpot.

11. Mechanism according to claim 10 in which the lvariable restrictions are apair of ball valves one of which opens for causing a more rapid flow of fluid into and out of said dashpot at the beginning of movement of said valve in either direction to initiate a reversal of fluid connections to the upper end of said engine cylinderl above direction, an escape passage,'a source of operating fluid under pressure, and an operating iluid line constantly connected to said engine cylinder on the rod side of said engine piston, said valve mechanism comprising, a tubular valve movable between an upper position to cause llow of lluid from said engine cylinder above said engine piston to said exhaust passage ,and a lower position to cause flow of operating iluid from said source to said engine cylinder above said engine piston, a llow chamber above and in communicationv with said engine cylinder above said engine piston through which chamber lluid llows to and from said cylinder and said source and said exhaust passage, a head on the lower end of said stem, said head lying in said ilow chamber, means in said flow chamber cooperating with said head to form a variable, annular orice therein for establishing a pressure differential between opposite faces of said head, piston extensions on the top and bottom of said engine piston, associated dashpots at the .top and bottom of said engine cylinder and cooperating with said piston extensions to retard the movement of said enginel piston near the limits of its stroke, whereby the pressure differential on opposite faces of said head in said flow chamber is changed when said engine piston reaches the end of its stroke and causes vertical movement of said head and said valve to shift connections `of said ow chamber and said engine cylinder above said engine piston between said source of operating fluid and said exhaust-passage.

13. Mechanism according to claim l2 in which the means in said flow chamber which cooperates with said head is so constructed as -toA restrict the variable annular orifice to its smallest areaA in intermediate positions of said valve whereby fluctuations in the rate of llow of fluid through such variable annular orice causes balancing movement of saidhead and compensating variations in such orifice.

14. In a hydraulic engine having a cylinder, a source of power iluid, a discharge, and a piston slidable in said cylinder, a reversing valve comprising, in combination, a slidable cylindrical valve body, a passageway controlled by said valve body` and open when said valve 'body is in a rst position for connecting one endv of said cylinder to said source, said valve body being biased by differential pressures to move toward a second position closing said passageway, a flow chamber in said rst passageway,

means in said flow chamber forming a llow restriction.

16.. A reversing valve according te claim ,14 ,in which the agrar/49 Yrnean's f'forming' a variable restriction f-is carried v-by f said valvev body-and the means responsive to thelpressureidrop across said restriction comprises a rpart fof said valve body.

17.vInfa hydraulicfeng-inehaving acylinder, a source of power fluid,'a dischargeand -alpistonf'slidable in said cylindenaf reversingvalve v-for alternately connecting saidv cylinder-to said sourceef powerdluidiinA a-iirstposition and said cylinderto saidl discharge ini al second =po`sition comprising, in combination, a recipro'ca'ble valve-body, means for establishing-a hydraulic force biasing said valve body toward the second positionandl-havingan element responsive toowofffluid from saidrsource of-power'uid to said cylinder'forh'olding said'Valve-b'o'dy in the `irst position-against such bias.

18. In a hydraulicenginefhaving-a cylinderandv a piston slidable therein, "a-reversing'valvefcomprising, ahousing, a cylindrical valve 'bodyre`cipr'ocably mounted inl-said housing, said 'bodybavingaf plurality o'fcircumferential portions of diierent diameters in sealing engagementwith portions. of'said housing, -'whereby/*said valve fbody land said housing form dilerential area surfaces' on saidtvalve body upon which pressure'fluid'c-:anact,al source-ofluid pressure, a passage controlled*by-saidfvalve in said housing connecting-said source swith saidtcylinder 'above 'said .4

piston, the-fluid 'pressure from l`said-sour`ce acting'on `said differential area surfaces-of said valve Lb'ody in aldir'ection to move said'valve to-apositionfclosing said-L passage, said valve body having a? portion'formingairesfrictionto the flow of fluidrfrom ysaid-source to'said cylinderwhereby a pressure drop is establishedbnsaid valve -body acting to retain said-body in alp'osition in-Awhich 'the cylinder `above the piston -is connected'vtolsaid sour'ce,and"means to reduce said pressure dropwherebythe valve-bodywill -move to a position'in which-said passage is closed.

19. A valve for controlling the -flow'of power fluid from asource tota consumer comprising azvalvefbody having two alternate ow-` controlling positions, a-passageway leading fromvsaid sourceltosaid-consumer, said passageway being controlled by'saidvalvefbody in its two positions, means for establishing abydrauliclforce on-said valve body acting in a direction tending to shift Vs'aid valve body from one position to the lalte'r'nate =position, means cooperating with said valvebodyto formzarestrictionto the flow of fluid to the consumer-andtherebyto establish a hydraulic force actingfonsa'idvalve fb'ody/oppositely to said first named hydraulicffor'cefformaintaining said valve body in said one position yWhere'bysflowofuid through sa1d restriction /abovea predetermined rate holds'said valve body in a positionto'di'r'ectHuidtoisaid-consumer 'i and a reduction 'of such'ow-below 'the predetermined rate reduces 'the second named-hydraulic iforce and V:the first named hydraulic force shifts said valve-body tothe alternate position. f

20. An automatically shifting three-wayvalve for "di- I' `tbodyl oppositely. sto l=said irst-named'ihydraulic force for :maintaining said fvalve body in its :irsti position, f, whereby flow of uid throughisaid restriction "in 'excess'of :afpre- `determined rate holds said-valve bodyzin'saidirstposition Hand Vasreduction.l of said ow below the predetermined rate reduces xthefsecondna'med .hydraulicforcenand the first-named l hydraulic force shifts fsaid valve :.body Y tof the -sec'ondi position todirect fluid from said enclosureto said discharge.

-21.`1In-a hydraulic enginefha'ving a cylinderyaisource of f power fluid, ya.' `discharge,`fand .faipiston slidable in said cylinder, a vreversing valve comprising, in combination,

'a slidable cylindricalk valve body, ,.-a;passageway controlled by'fsaid valve=body and open when said valve bodyis in fa' first'po'siti'on for connectingone'endof 'said cylinder to rsaid s0urce,said valve'body being biasedibyf'diierential pressures li-to =move towardfa' second position. closing said passageway, meansin vsaidpassageway forming a 'flowfrestriction therein, meansi'responsivefto. pressure drop La'cross said v:restriction ifor holding fsaid "valve 'body `in 1 said? rstfp'osition s withisaid :passageway: open, iand a second passageway controlled by said valve body ,andopen :when/said valve'body' is yinwfsiich second position Vfor connecting said end ofy rsaidfcylinder to discharge.

'22.In1a hydraulic engine'havingfafcylinder, afsource -of-p'owerffluid, 'af--discharge, and fa piston 'slidable :in said cylinder, a reversing valve comprising, in combination,

A a slidable cylindrical :valvebody,faffpassageway. controlled -by said `valve bodyfandopen when saidsvalve bodyis'in -a iirst'iposition for connectingronexendof said cylinder 'to saidtdisch'arge,vsaidf,valve bodybeing biased :by differential pressureswto movetowardta .-secondfposition closingfsaidip'assageway, f-meanswn ysaidsipassagewayfformfing a `flow vrestriction therein, zmeansfresponsive to pressure drop across :said restriction? forfholdingysaid valve body in said `first @position twith zsaid passageway open, -and-la secondlpassageway controlled by'said valve ,body and-'open when -said valve body. is. i'n suchsecondwposition forY connecting' said end of saidcylinder -tofsource.

, 23.-'In1a' hydraulic engine 2having acylinder, aisource of powerffluid, a discharge,` and ia piston-slidable in said y'cylinde'igfa reversing valvelhaving two opposite 'operative positions i in f one of l which said cylinder '-is connected `to said source'a'ndin the other -of'fwhichlsaid .cylinder fis connectedito said discharge',m`eansfor:establishing a hydraulic "force lbiasing lsaid. 'valve 1 `towards the opposite of the positions in Whichlit fzstands during operative strokes *ofl said Ypiston, and: saidvalve having'ranV element responsive -to apressure dropvcaused'by iiow.' of fluid 'into 'and out foffsaid cylinder fforholding said valve in lposition 'against such biasinglhydraulicfforce, :whereby'vsaid -valvereversesits position-fand-moves to an oppositeposition'lwhenev'er said holding force s is reduced by ta reducvrtionin '-floW below'fat-predetermined rate.

v.References Cited iinf thed iilei of this :patent UNITED -STATES PATENTS '2,100,092 Tear ;N0'v..23, 1937 2,448,557 Stephens Sept. 7, 1948 2,541,958 Dear'dorfr et a1. Feb. 13, v1951 2,598,891 rCooke 'June 3, 1952 2,615,433 Deardorl et al. *'Oct. Y28, 1952 2,682,257 cDeitricksori VJunev 279, 1954 f FOREIGN .PATENTS 640,642 :Great Britain ..=Apr.l 4, 1947 992,359' France :=June A11, 1951 

